What do oral pills contain and how do they act as effective

What do oral pills contain and how do they act as effective contraceptives?

Oral contraceptive or pills are either progestogens or progestogen-oestrogen combinations.
They function as contraceptives by
(i) inhibiting ovulation.
(ii) inhibiting implantation,
(iii) altering the quality of cervical mucus to prevent or stop the entry of sperms.