I cant find anything in the guide book or in game.
Can someone explain what exactly Burrow does?
Brood War Burrow
✔ Make the unit invisible to opponents, unless they reveal the area with detection.
✔ Allow lurkers to attack. Lurkers can only attack when burrowed; but like other Zerg units, lurkers need to unburrow to move. It's nice to mention Stop Lurkers, because the technique is a direct result of lurkers not being able to move while burrowed.
✔ Provide reduced vision. Burrowed units will have their vision reduced (it be interesting to measure how much), but they're invisible, so they're essentially poor-man's observers.
✔ Obstruct buildings. Although opponents cannot see the burrowed unit without detection, they will be unable to build or land buildings on top of the unit.
✔/✘ Stack units [PATCHED in 1.15] (Thanks to Decency for reminding me!). Used to be able to quickly burrow, unburrow, move together and the units would become stacked. Good thing you can't anymore because it was way more powerful than stacked mutas.
✘ Allow units to move. Zerg units able to burrow must unburrow to move.
✘ Avoid splash damage. Burrowed units can be killed by splash damage alone, usually by seige tanks, reavers or archons.
✘ Avoid damage from or effects of spells. Psi-storm's gonna getcha. So will other spells including
plague (pending testing), ensnare, maelstrom (just for lulz XD), disruption web and EMP (although EMP won't do anything).
✘ Avoid spider mines. Yeah, spider mines aren't detectors (they don't reveal cloaked or burrowed units), but for some reason they still attack cloaked and burrowed units.
✘ Regenerate health faster. This is a misconception since health regen is variable in SC2, and especially since roaches regenerate faster while burrowed. Units and buildings (with the exception of eggs) all regenerate health at 0.372 hp/s or 1 hp per 2.685 sec, regardless of whether they are off creep, on creep or burrowed.
You can check out the Starcraft wiki that I've linked for more information, but other than healing quicker, units that are burrowed are invisible to your opponents. This can lend itself to, among other things, leaving scouts at choke points or resources and setting traps for your opponents.
Burrowed units are also unable to move while burrowed.