A 4 in 1 is actually a cat vaccine.
It vaccinates against FVRCPC:
FVR -Feline viral rhinotracheitis
C - Calici virus
P - Panluekopenia
C - Chlamydia
A 5 in 1 is a dog vaccine and vaccinates against DHPP
D - Distemper
H - Adenovirus types 1 & 2 (includes Hepatitis)
P - Parainfluenza
P - Parvovirus
If you add Lepto, that makes the 5 in 1 a six in one (6 in 1), DHPP4L (4 strains of Lepto protected against).