Milonga
The social tango event itself. Also a faster tango rhythm — context tells you which.
Tanda
3–4 songs by the same orchestra. You dance the whole tanda with one partner.
Cortina
Short non-tango music between tandas. Clear the floor, find a new partner.
Cabeceo
The eye contact + nod invitation system. No walking across the room to ask.
Ronda
The counter-clockwise line of dance. Everyone moves in the same direction.
Practica
Informal practice session — more relaxed than a milonga, fine for beginners.