When comping you want your chords to flow smoothly from one to another, instead of bouncing around on the guitar neck. Each note of a chord is a voice. Voice leading is moving individual chord voices smoothly from one chord to the next.
Voice leading is not only useful in comping though. In single note improvisations voice leading can function as a skeleton on which you can base your lines on.
Let's have a look at some examples for voice leadng in 2 5 1 chord progressions. The first one is a possible voice leading for a 2 5 1 progression in C major:
There are 2 voices in this example: the blue one and the orange one:
Fill this example in with some other chord tones and a bit of chromatism and you get this:
The next example starts on the 5 of Dm7, goes to the b9 of G7 and to the 5 of Cmaj7.
Here are some voicings you can use with this voice leading:
Here's antoher example, this time for a 2 5 1 progression in Gmaj. The voice leading starts on the 9 of Am, goes to the b13 of D7, to the 9 of Gmaj and finally to the 7 via the 1.
Here are the voicings for this voice leading:
All examples until now had a descending voice leading. Of course you can also make an ascending voice leading. The following example is in C major again and has 2 voices.
Voice leading gives your improvisations more chartacter, it's like your lines have a story to tell. Now try to find some lines of your own.