What affects bond angles?
Bond angles mainly depend on the following three factors:


Hybridization: Bond angle depends on the state of hybridization of the central atom
Hybridization: $\ce{sp^3}$, Bond angle: $109^\circ$, Example: $\ce{CH4}$
Hybridization: $\ce{sp^2}$, Bond angle: $120^\circ$, Example: $\ce{BCl3}$
Hybridization: $\ce{sp}$,   Bond angle: $180^\circ$, Example: $\ce{BeCl2}$
Generally s- character increase in the hybrid bond, the bond angle increases.
Lone pair repulsion: Bond angle is affected by the presence of lone pair of electrons at the central atom. A lone pair of electrons at the central atom always tries to repel the shared pair (bonded pair) of electrons. Due to this, the bonds are displaced slightly inside resulting in a decrease of bond angle.
Electronegativity: If the electronegativity of the central atom decreases, bond angle decreases.


Good Side note:

Triple bonds repel other bonding-electrons more strongly than double bonds.
Double bonds repel other bonding-electrons more strongly than single bonds.

Heres a nice read into the different components (extra)