ETSI NOS stands for "European Telecommunications Standards Institute Network Operation System". It's basically a set of rules and guidelines that help people who work with technology and telecommunications systems make sure everything works together properly.
Think of it like building with blocks. If you want to build a tower with different kinds of blocks, you need to make sure they fit together properly or the tower might fall over. ETSI NOS helps people who work with technology and telecommunications systems make sure the different parts and pieces fit together properly.
For example, if you're building a tower with blocks, you might need to make sure the pieces snap together securely. If you're working with technology and telecommunications systems, you might need to make sure different computer programs can talk to each other and share information correctly.
ETSI NOS is a way for people who work with these systems to communicate and make sure everything works together smoothly. It's kind of like a set of instructions for building something really big and complicated.