What does the Chinese word “我明白” mean in English?
It means “I understand”. However, do not confuse this word with 理解， which also means to understand. The thing about Chinese words is that where in English, they use the same word for similar concepts, Chinese has completely different words for them, since these words carry different attributes.
Whereas 明白 carries the meaning “I see”, 了解/理解 carries the meaning “I fully understand”. For example, when reading through a document and everything makes sense to you, you would use 我明白; if you read through the same document and you understand all the intricacies and everything there is to know about it, you would use 了解/理解。
Another example:
Let us take the word “to think”, and translate it into Chinese in different contexts.
“I think he is at the store.”
In this context, you would use the word 觉得 (jue de), which, in this situation, has the attribute “to believe, to think”—“I believe he is at the store.”
“He was thinking about food all day.”
In this context, you would use the word 在想， which carries the attribute “to bear in mind, keep mind, ponder about— “He kept food in mind all day.”
“I’ll think about going to China.”
In this context, you would use the word 认为， which carries the attribute “to consider, to judge something”— “I’ll consider going to China.”