leftmost and rightmost derivations

RGPV 2020   
What are leftmost and rightmost derivations? Explain with suitable example ?

Grammar:

S → aS / ∈
For generating strings ‘aaa’.

Left most derivation: 

A leftmost derivation is obtained by applying production to the leftmost variable in each step.
S → aS
→ aaS       (Using S → aS)
→ aaaS     (Using S → aS)
→ aaa∈
→ aaa

Right most derivation:

A rightmost derivation is obtained by applying production to the rightmost variable in each step.
S → aS
→ aaS       (Using S → aS)
→ aaaS     (Using S → aS)
→ aaa∈
→ aaa