Much of Live's unique interface comes from being designed to use in live performance as well as for production. As such the interface is more compact than most sequencers and clearly designed for use on a single screen. There are few pop up messages or dialogs. Portions of the interface are hidden and shown based on arrows which may be clicked to show or hide a certain segment (e.g. to hide the instrument/effect list or to show or hide the help box).
The arrangement view in Ableton Live 6.
There are two views which are central to Live – the arrangement view and the session view. The session is primarily used to organize and trigger sets of sounds called clips. These clips may be arranged into scenes which may be triggered as a unit. For instance a drum, bass and guitar track might comprise a single scene. When moving on to another portion of the composition – a new scene – some or all of those parts might differ and could be triggered in parallel. In Live 6, there is also the addition of "racks" which allow the user to easily group instruments and effects.
The other view is the arrangement view, which is used for recording tracks from the session view and further manipulating their arrangement and effects. This view is fairly similar to a traditional software sequencer interface.
Clips may either be an audio sample or MIDI (triggering one of Live's built in instruments, third party VSTs instruments or external hardware). Live comes by default with two instruments – Impulse and Simpler.
Impulse is a more or less traditional drum sequencing instrument which allows for defining a kit of up to eight drum sounds. There are a number of options available for preprocessing these samples such as basic equalization, attack, decay, pitch shift, etc. Once the kit is defined these samples are arranged into groups of measures using a piano-roll interface.
Simpler is a relatively easy to use sampling instrument. It is based on working with a single sample, applying preprocessing and then arranging it in a piano roll interface. In this case, rather than the notes representing different samples as in Impulse, the samples are pitch shifted to the selected note.
There are a number of additional instruments which may be purchased separately or as part of the Ableton Suite. 
Sampler is an enhanced sampler.
Operator is an FM synthesizer.
Electric is an electric piano instrument.
Tension is a string physical modelling synthesiser.
Analog simulates an analog synthesizer.
Drum Machines is a collection of emulators for classic drum machines.
Session Drums is a collection of sampled drum and percussion instruments.
Essential Instruments Collection is a large collection of acoustic and electric instrument samples.
Orchestral Instrument Collection is a collection of four different orchestral libraries, which can be purchased individually or as a bundle. They are as follows: Orchestral Strings, Orchestral Brass, Orchestral Woodwinds and Orchestral Percussion. The Orchestral Instrument Collection is not included in Live Suite.
Most of the effects are fairly familiar effects in the digital signal processing world which have been adapted to fit Live's interface. They are however fairly obviously tailored for the target audience of Live – electronic musicians and DJs – rather than, say, post processing a guitar rig.
The audio effects shipped with Live (version 6) are:
Ping Pong Delay
Additionally there are a handful of MIDI-only effects including arpeggiator, chord, pitch, random, scale, and velocity. In more recent versions Live is also able to use VST and Audio Unit (AU) effects.
Working with audio clips
Sasha performing using Ableton Live with Macintosh computers.
In addition to the instruments mentioned above, Live can work with samples. Live attempts to do beat analysis of the samples to find their meter, number of bars and the number of beats per minute. This makes it possible for Live to shift these samples to fit into loops that are tied into the piece's global tempo.
Additionally Live's Time Warp feature can be used to either correct or adjust beat positions in the sample. By setting warp markers to a specific point in the sample, arbitrary points in the sample can be pegged to positions in the measure. For instance a drum beat that fell 250 ms after the midpoint in measure may be adjusted so that it will be played back precisely at the midpoint.
Some artists and online stores[specify] now make available mp3 files that are pre-adjusted, with tempo information and warp markers added. The mp3 file or files are accompanied with a file in Live's native format
Almost all of the parameters in Live are controlled by envelopes which may be drawn either on clips and will be used in every performance of that clip or into the arrangement so that they vary at different points in the playback of a composition. The most obvious examples are volume or track panning, but these are also used in Live to set things like the root note of a resonator or the delay time or feedback amount for a delay effect. Essentially these map to most of what would be a knob on an effect in a traditional audio processing rack and in fact they may be mapped to knobs on MIDI controllers.