Transformer encoders are not really popular anymore, and all the top LLMs are decoder-only architectures. But encoder models like BERT are used for some tasks.

Transformer encoders are not really popular anymore, and all the top LLMs are decoder-only architectures. But encoder models like BERT are used for some tasks. In any case, self-attention and MLP is the crux of Transformer blocks, be they in the decoder or the encoder.