How is this tensorflow command interpreted?

I am reading an introductory tutorial on tensorflow here, and I'm confused about the code that defines an input layer for a word2vec embedding:

# Headline input: meant to receive sequences of 100 integers, between 1 and 10000.
# Note that we can name any layer by passing it a "name" argument.
main_input = Input(shape=(100,), dtype='int32', name='main_input')


Afaik, there are 10.000 words in the library, and the input is a string of 100 words (a news headline). One word is represented as a 32 bit int.

But it seems to me that too little information is passed to this Input layer:

• What does "shape=(100,)" mean? why does it omit the second argument?

• how does it know how to deal with "dtype='int32' "? If I saw that without context, I would guess that it interprets each of the 100 32bit ints as numbers rather than one-shot word vectors, so I would guess it would create a 100 neuron layer, where each neuron receives 1 input of 32 bits which would be the input to the neuron's activation function. But what we really want is a neural net with 10000 neurons (one for each word) times 100 (for each word in the sequence), right?

What am I missing?