ChaCha20-Poly1305 and AES-GCM are both authenticated encryption algorithms used to secure data in transit. They are designed to provide confidentiality and integrity of data. However, they differ in their underlying structures, performance, and implementation.

1. Underlying Structure: ChaCha20-Poly1305 is a combination of two algorithms: ChaCha20 for encryption and Poly1305 for message authentication. ChaCha20 is a stream cipher based on the Salsa20 family of ciphers, while Poly1305 is a 1305-bit MAC (Message Authentication Code) algorithm. AES-GCM, on the other hand, is a mode of operation for the Advanced Encryption Standard (AES) and uses the Galois/Counter Mode (GCM) for both encryption and message authentication. AES-GCM is based on the AES block cipher, which is a substitution-permutation network (SPN) design.

2. Performance: ChaCha20-Poly1305 is faster than AES-GCM, making it a preferred choice for low-power devices or when high-speed performance is required. ChaCha20 is particularly efficient on modern processors due to its simple structure, while AES-GCM has higher computational requirements and may be slower on certain hardware.

3. Security: Both ChaCha20-Poly1305 and AES-GCM provide equivalent security levels. They use a 128-bit key size, and both have been thoroughly analyzed by the cryptographic community. There are no known attacks that could compromise the security of either algorithm.

4. Implementation: ChaCha20-Poly1305 is simpler to implement compared to AES-GCM. The structure of ChaCha20 is based on a simple and fast algorithm, making it easier to code. AES-GCM, on the other hand, has a more complex structure due to its use of a block cipher in combination with a message authentication code.

5. Standardization: ChaCha20-Poly1305 is not an official standard, while AES-GCM is a standardized mode of operation for the AES algorithm, making it more widely adopted and supported by various software and hardware implementations.

In conclusion, while ChaCha20-Poly1305 offers faster performance and simpler implementation, AES-GCM benefits from standardization and broader support. The choice between the two depends on the specific requirements and constraints of your application.