A build is a piece of software or Product which consists of a set of features and a few bug fixes,
Build is internal for testers to test and log defects.
A build can go from build-1 to build-n, So basically it is a growing application in simple terms,
The first build will have a few requirements and features in it that may require a unique perspective. Lets say 10% of the software is developed. The next build will have bug fixes (ie. errors in first build is fixed) and also some new features are added. So lets say its now 20% of software is developed, this process continues till 100%, ie. Until Build is stable.. Implies no bugs or very few bugs and all features have been developed. Which means it is a complete software, which is ready to use.
A release is again a piece of software that consists of set of stable builds pushed to production,
so basically release decides how many features we are delivering to client or pushing to production. Even release of the product is not the final, release is also ongoing, some companies may release monthly, quarterly or yearly depending on the client need, as clients cannot wait till all features are developed and the company developing the software can develop the next few features after the First Release (Software with basic features / Requirements of the client that has been satisfied)
Client requirements always an on going one, so depending on the complexity and priority of requirements, organisation or team decides the duration of each build or release.