Is the SHA1 hash of MD5 hash of a password secure? Cryptography is not my area, so pardon me if the question is annoying.

Some time ago, I implemented an Internet site, which database had a users table. To keep the password in its user table field, I used

encrypted_password= sha1(md5(raw_password));


What are the pros and cons of the approach I used?
Pros: The only pro is that your method is very slightly better than storing passwords in plaintext.

Cons: If an attacker gains access to your database, he will easily be able to recover 99% of passwords with only a bit of work, and he won't even need anything more than a laptop.

The lesson here is the usual one. Never build your own crypto. Use a secure password hasher like Argon2. All the information you could need on secure password hashing can be found in this post.

Also, a minor nitpick: "encryption" is not the term you are looking for. Encrypting a value implies a transformation that is invertible, e.g. the result can be decrypted to recover the original value. Hashing, on the other hand, implies a one-way transformation that cannot easily be reversed (other than trying all possible inputs and checking the result).