Where are holding patterns at?
Wherever a controller feels like putting one. A corner of the pattern will always be on some sort of fix, be it a VOR, NDB, intersection, DME
fix, GPS waypoint, etc.
Do planes just make 360s around a VOR?
Holding patterns are racetrack courses with the standard length of the inbound leg being 1 minute when below 14,000 MSL, and 1.5 minutes when above 14,000 MSL.
Turns are normally made to the right.
Speed limits are:
200 KIAS <= 6,000 MSL.
230 KIAS 6,000 < you <= 14,000 MSL
265 KIAS > 14,000 MSL
When entering from sector (a), the parallel entry is executed, turn outbound, proceed for 1 minute (or 1.5 for the appropriate altitude), and then turn around on the protected side and intercept the inbound course or proceed to the holding fix.
When entering from sector (b), a teardrop entry is executed. Turn to a heading that is 30 degrees to the protected side of the outbound course, proceed for 1 (or 1.5) minute, then turn and intercept the inbound course.
When entering from sector (c), a direct entry is executed. Turn to the outbound heading, fly for one minute, and turn to intercept the inbound course.