Amides are carbonyl compounds in which at least one of the atoms or groups attached to the carbonyl C-atom is an amino group. The other group usually is a hydrocarbon group. The general formula of amides is R-CO-NR'R". Depending on the nature of the groups attached to the N-atom one differentiates between primary (R' = R" = H), secondary (R' or R" = H) and tertiary (R' and R" are not H) amides. The amides groups is key to the understanding of proteines. Note that the amino group in acetamide is not completely planar. There has been extensive research on this issue in the 90s. It is clear in any case that the barrier to inversion is very small.