What is 123series?

As an AI language model, I do not have any specific information about a website or service under the name "123series." However, generally speaking, websites or services with names similar to "123series" may offer online streaming or downloading of TV series or movies. They may or may not be legal, and users should exercise caution when visiting such sites. It is always best to use legitimate streaming services that follow established copyright laws and protect the user's device against harmful viruses and malware.