The first stage of second language acquisition is the silent stage. It can also be referred to as the receptive stage. This happens a the very beginning of language learning, when the language learners haven't got the skills yet that are needed to actively use the language themselves. Instead, they are spending time learning basic things, such as vocabulary and grammar, which will enable them to move up to the next stage.
The second stage is the early production stage. This stage does not take place silently anymore, as learners have now acquired sufficient vocabulary in order to be able to produce short sentences or utterances.
The third stage is the stage of speech emergence. Here, first dialogues might be taking place. For example, a learner might be able to ask for someone's name and give their own name when being asked.
The fourth stage is called intermediate fluency. At this stage, a language learner has acquired a lot of vocabulary and is able to formulate more advanced sentences, which include not only a wider range of vocabulary but also a wider range of grammatical structures.
The fifth stage is usually referred to as continued language development. This is the final stage of language learning. Here, learners keep using their knowledge of the language to develop even more fluency and mastery of the language with the goal of maintaining it long-term.