By using Move 5 to secure their own corner, Black is trying to get some “cash in the bank” - i.e. quickly secure one large corner that will be difficult for you to invade. Since they also have the Q16 stone on the right, they are probably aiming at creating a large extension across the top.
As such, approaching from the outside at R14 is kind of risky because if they respond with The Kick joseki - they could secure the top with only a few moves (Black R15, White Q14, then Black O16 to settle). Your better options may be
- Prevent a large extension - by playing at O17 or L16
- create a large extension - by playing K3 or something similar on the bottom
I feel like this 19X19 FOR BEGINNERS article may help you make sense of the opening dynamics: PLAYING A BALANCED OPENING
Good luck!