Answer 1

Basically string is sequence of characters.
Characters consists.
*Alphabet : a...z, A... Z
*Numbers: 0.....9
*special symbols:*/+-,!=?":#)$@-_[]{}<>&_%|\•~ any more.
If you combine characters it's called string.
Your name is also string 'Abhay'.
Let's discuss about commands.
Lower makes selected string lower case.
Lower('ABHAY'); will output abhay
Upper makes selected string uppercase
Upper('abhay') results in ABHAY.
Remember that sql isn't case sensitive so you can write you function name in any case like
LOWER or lower or Lower etc.
You can create entire column uppercase or lowercase using these functions.
Happy learning