1. 'Let' can mean 'allow' or 'give permission'.
ex : वो मुझे घर जाने देता है - He lets me go home.
2. We can also use 'let' to mean 'allow' in the sense of 'make something possible':
Ex : उसे खुद फैसला लेने दो - (You) Let him take the decision himself.
3. Let's + infinitive is often used to make a suggestion:
ex : Let's get some coffee - चलो कॉफी पीते हैं।