L is the least amount of error correction. A QR code created with level L can be read even if 7% of the QR code is unreadable.
M provides more error correction – 15% of the QR code might be unreadable but it will still work.
Q provides still more error correction, up to 25% of the QR code might be unreadable and still work.
H provides the most error correction, with up to 30% of the QR code being unreadable but still working.