A Word-for-word translation is a translation of language in one language to another language, one word at a time. The nature of this is that it retains the grammar of the first language but with the vocabulary of the second.
For example, consider the Chinese sentence 我 每天 和 朋友 在 餐厅 吃饭 (in Pinyin: Wǒ měitiān hé péngyǒu zài cāntīng chīfàn). The English translation of this is "I eat at the restaurant with my friends every day" (some minor variations are possible). However, the word-for-word English translation is *"I every day with friends at restaurant eat". As an English sentence, it is ungrammatical, but nevertheless comprehensible and this is broadly similar to Chinese learner English because Chinese learners' interlanguage tends to be influenced by their L1 grammar due to L1 transfer.
Turning this around, we can start with the English sentence "I eat at the restaurant with my friends every day" and change this word-for-word into Chinese, producing *"我 吃饭 在 [the] 餐厅 每天 和 朋友" or *"Wǒ chīfàn zài [the] cāntīng měitiān hé péngyǒu". Note that the definite article has not been translated because Chinese lacks an equivalent. This is also ungrammatical but comprehensible to a Chinese speaker, but it may provide them some insight into the structure of English better than e.g. This sentence is "subject + verb + prepositional phrase adverbial (preposition + definite article + object of a preposition) + noun phrase adverbial (adjective + noun)".