Checksum vs. Hash: Differences and Similarities ? What are similarities and differences between a "checksum" algorithm and a "hash" function? 

Can they be used instead of each other? Or their usage are different?

For example, for verifying the integrity of a text, which one is better to be used?
Sometimes these terms are used more or less interchangeably.  Traditionally, a checksum is used to detect corruption and a hash is used to map large elements into slots randomly.  In Bitcoin-land we're often concerned with "cryptographic hashes"  which are hashes that have special security properties.

Things called checksums are usually designed to have certain uniformity properties that make them maximally likely to detect errors.  Things called hashes are usually designed to be very fast to compute and not be too non-uniform.  Things called cryptographic hashes are designed to make it difficult to compute a collision.

The security properties of cryptographic hashes often make them slower and less uniform than functions you would use for cases where the security isn't required.

Generally any function from any of the three groups could be used in any of the applications, the result would just not achieve the security, performance, or reliability that you'd get for using the right tool for the job.