First of all, this is not an "optional" topic. Students tell me, "Oh--I don't play reverses." This is not acceptable. It is equivalent to saying: "I don't play rebids by opener."

A "reverse" is when opener's rebid (2nd bid of the auction) meet both A & B:

A) Is in a HIGHER ranking suit than his first suit

B) Is at a HIGHER level than responder's response

So, these are reverses:

1-1-2
1-1-2
1-1-2
1-1NT-2any
1-1-2
1-1NT-2M

What do these bids show? First of all, they are natural. The opener will have (typically) at least 5 cards in the suit he opened and at least 4 cards in the suit he bid next. He will not have a flat/balanced hand (he would have rebid or opened in notrump).

What strength? Enough to be at the three level. So, Invitational or better. About 17+ counting useful distribution.

Forcing? Yes, a reverse is forcing. The opener's partner must bid again. He cannot pass. But, the reverse is not forcing to game. It shows about 17-20.

Note: A reverse is not the same as a jumpshift. A jumpshift is a jump by opener in a new suit. Opener's jumpshift would be:

1-1-2 of a Major
1-1-2
1-1-2
1-1-3
1-1-3 of a minor
1 MAJ-1NT-3 of a lower suit

Opener's jumpshift is GF (and natural).
Opener's Reverse is not GF, but shows extra and is natural.

Note: Do not make a jumpshift reverse (such as 1-1-3). It is one or the other. A jumpshift or a reverse. Never a choice between the two.

Followups after Opener's Reverse (alert: requires study/memory)

After, say 1-1-2, I recommend:

2= 5+ spades, 1-round force
2NT=Forcing, but could be a weak hand (responder can pass opener's next bid). Denies 5+
3=Natural, Forcing
3=Natural, GF (some decent values)
3=Natural, GF 4 hearts
3=Natural, good suit, forcing
3NT=Natural, some extras, but no real slam interest.

The generic summary of the above auction would be as follows:
After opener's reverse:

Responder's repeat of his suit=5+, one-round force
2NT=Potentially a weak sign-off type of hand
3-level=values, GF

Remember that in LC Standard, 2/1 auctions are not part of the reverse discussion. 1-2-2 can be a dead minimum. However, if the auction starts 1X-1Y, then opener's 2Z in a higher suit than his first suit is surely a normal reverse, promising extras.

You might also consider Larry's Webinar on Reverses which you can find HERE.

Further Reading:
What Should we Play