What's the difference between mind (citta) and mental activity (cittasaṅkhāra)?

Hello !

MN 44 says:

Recognition and feeling are mental phenomena bound to the mind; therefore recognition and feeling is mental activity.” (Ven. Suddhāso)

Saññā ca vedanā ca cetasikā ete dhammā cittappaṭibaddhā, tasmā saññā ca vedanā ca cittasaṅkhāro”ti.

I’m having trouble understanding the difference between citta and cittasaṅkhāra. Understanding the difference is important for correctly practicing Anapanasati tetrad 2 and 3, since tetrad 2 notably speaks of cittasaṅkhāra, while tetrad 3 speaks of citta.

Concretely someone who turns his attention away from cittasaṅkhāra to only contemplate citta, what mental phenomena does he have to start contemplating? Hypothetically, he who contemplates citta no longer contemplates perception and feeling (based on MN 44, since perception and feeling belong to cittasaṅkhāra, not citta) ; but what does he contemplate? Volitions ? Or consciousness? Or both?

Thanks in advance,

May all beings rely on dhamma friends