saṅkhāra = san + kara where san is the good and bad things we acquire and kara is the act of doing, so saṅkhāra is the action done with san, thus saṅkhāra is an intentional action that carries kamma.
saṅkhāra are the fifty cetasikas (good and bad) minus vedanā and saññā.
Here is the list of 52 cetasikas (mental factors) at a glance .