Those sets of letters and numbers are an "old school" notation for our moves.

Lets look at my last move:
B-K3
It consists of the piece being moved
 a hyphen and the square we are to move to

Fine, what do the letters and numbers actually mean?

There is a standard notation for each piece:

IIRC

K = King
Q = Queen
R = Rook or Castle
Kn = Knight
B = Bishop
Pn = Pawn

So the Letter is the piece to be moved, then the hyphen, finally the Letter and Number combination describes as follows Letter is the Left/Right position
sort of like Longitude on a map. Each Piece has a starting position and this is the name of that column.

Again the same example:

B-K3

K3 means the King's column.

The number denotes the UP/DOWN relation sorta like Latitude on a map

So, K3 is King's Column, third row.

Makes much more sense when you are looking at a board .