は

は marks the topic: what the sentence is about. Everything after it is a comment on that topic. 私は学生です is "as for me, (I'm) a student."

As a particle it's pronounced wa, but it's still written with the kana は (ha), a leftover from older spelling.

A topic is usually something already known in the conversation, or something general: 猫は魚が好きです, "cats like fish". Once a topic is set, Japanese keeps it without repeating it, which is one reason subjects seem to vanish from sentences.

は versus が is the classic beginner puzzle. For now: は for what you're talking about, が (later in this deck) for who does something or what exists, especially when it's new information.