Difference : subsequences and substrings

What are the differences between subsequences and substrings?

• the question makes sense to me and has been answered, need it be on hold? – Andrew MacFie Apr 17 '15 at 18:16
• @AndrewMacFie, voted to re-open. – goblin Nov 5 '17 at 7:34

Substrings are consecutive subsequences. For a $n$-element sequence of pairwise distinct letters you have $n(n+1)/2$ non-empty substrings and $2^n-1$ non-empty subsequences.
I hope this helps $\ddot\smile$