explain me the concept of SN1 and SN2 reaction with mechanism???

SN²-bimolecularnuclophilic substitution reaction and SN1 is unimolecularsubstitution reaction.

for SN2

R-Cl+Nu^------->R-Nu+Cl^-

eg:CH₃-Cl+OH- ---->CH₃-OH+CL^-

Rate depends on concentration of CH₃-Cl and OH^-

its order of reactivity is primary>secondary>tertiary

here strong base is used

it occurs in single step

intially the bond between CH3 and Cl is broken and OH- is added to Ch3

For SN1

tertiary alkyl halide reacts with weak base

rate depends on concentration of alkyl halide

here order of reactivity is tertiary>secondary>primary

it occurs in two steps

intially tertiary carbocation is formed and in second step  nucleophile is added

note: i cant write equation for SN1 due to bond representation between carbon

i also wanted sn1 and sn2 mechanism...please explain me with the help of mechanism