Transform: Transform is, as the name implies, a move that allows the Pokémon to transform into the opposing Pokémon and copy it's stats, abilities, and moves. It's the only move that Ditto can learn.

Does imposter Ditto copy abilities?

Imposter copies the target's appearance, cry, moves (which all have 5 PP), Ability, stats (except HP), stat changes (but not stat multipliers such as with Choice Specs), weight, and Mega Evolution or form (regardless of held item).

Does Ditto transform copy status?

Ditto, when transformed, will always copy the stats of the opponent (except for its HP, which it keeps), regardless of level. So yes, Ditto would have the awful stats of a level 2 Pidgey (except for HP).