What is the difference between surd and indices?

A surd is when you have a number that is irrational or in other Word, A number that its number cannot be square rooted e.g. A square root of 2,3,5 etc, on the other hand an indices are numbers that are cubed or squared for instance 3³ ('3 cubed' or '3 to the power of 3') and 5² ('5 squared' or 5 'to the power' of 2) are example of numbers in index form.

3³ = 3×3×3

2¹ = 2

2² = 2×2

2³ = 2×2×2

etc.

The ² and ³ are known as indices. Indices are useful (for example they allow us to represent numbers in standard form) and have a number of properties.