Watch the Basic Eight online guitar lesson by Chris Buono from Guitar Lab: Blues Soloing
Basic Eight is all of eight bars long. A dead giveaway that this is the case is the IV chord showing up in bar 3 as opposed to, say, a quick four" or "quick to four" instance where the IV chord drops in bar 2. Before you assume these changes will just fly right by you, relax - an eight bar blues is actually a lot easier to adapt to than the longer 16 bars we just checked out or the oddly, yet even numbered 14 bar blues awaiting you later in the course. Just ease into it and you'll be rockin' it in no time.