は is the hiragana for "ha". However, when は is the topic marking particle, it is pronounced "wa" for reasons unknown to pretty much everyone. Now in the future, you shall see sentences like this:
Seika wa hito desu.
Seika is a person.
は is marking Seika as the "topic" of the sentence - when literally translated to English, most professors agree that it should be translated something like "As for Seika, he is a person". Just because は is marking something, it does not necessary mean that it's the subject of the sentence. It is what the speaker is talking about. は also serves to emphasize the predicate of the sentence, drawing attention away from Seika and more towards the fact that he is a person. Taken from japanese.about.com " 'wa' is used to mark something that has already been introduced into the conversation, or is familiar with both a speaker and a listener." Now look at this sentence:
Seika ga hito desu.
Seika is a person.
Here, が marks Seika as the "subject" of the sentence - the sentence is actually Seika is a person. It is emphasizing the subject, bringing attention to the fact that it is Seika that is a person. Taken from japanese.about.com " 'ga' is used when a situation or happening is just noticed or newly introduced."
Usually, Japanese books tend to skim over the differences between wa/ga and just use wa to mark the subject at first, but that's just confusing and wrong. So always remember は is the topic marker, not the subject marker, and can mark other things. Using the "As for ____" format for は is usually helpful.
Moving on to です - as I said before, it is an equal sign, not a verb. It does not mean "to be", which is reserved for two other verbs which will come about soon. I'm not sure how to explain it...it is used when convenient. ^^; For the above sentences, the desu is setting Seika equal to person - Seika=person. It can be used in many similar sentences:
Maru wa otoko desu.
Maru is a man.
Shunsuke wa kakkoii desu.
Shunsuke is cool.
I don't think there's really anything more to be explained about desu...at least not yet. ^^; So that ends lesson 3!