What are N-Grams?

N-grams of texts are extensively used in text mining and natural language processing tasks. They are basically a set of co-occurring words within a given window and when computing the n-grams you typically move one word forward (although you can move X words forward in more advanced scenarios).

For example, for the sentence “The cow jumps over the moon”. If N=2 (known as bigrams), then the ngrams would be:

the cow
cow jumps
jumps over
over the
the moon
So you have 5 n-grams in this case. Notice that we moved from the->cow to cow->jumps to jumps->over, etc, essentially moving one word forward to generate the next bigram.

If N=3, the n-grams would be:

the cow jumps
cow jumps over
jumps over the
over the moon
So you have 4 n-grams in this case. When N=1, this is referred to as unigrams and this is essentially the individual words in a sentence. When N=2, this is called bigrams and when N=3 this is called trigrams. When N>3 this is usually referred to as four grams or five grams and so on.

https://kavita-ganesan.com/what-are-n-grams/#.YJbvEbVKiPo

Statistical language models, in its essence, are the type of models that assign probabilities to the sequences of words. In this article, we’ll understand the simplest model that assigns probabilities to sentences and sequences of words, the n-gram.

You can think of an N-gram as the sequence of N words, by that notion, a 2-gram (or bigram) is a two-word sequence of words like “please turn”, “turn your”, or ”your homework”, and a 3-gram (or trigram) is a three-word sequence of words like “please turn your”, or “turn your homework”

https://towardsdatascience.com/introduction-to-language-models-n-gram-e323081503d9#:~:text=You can think of an,%2C or “turn your homework”

Other good reads:
https://en.wikipedia.org/wiki/N-gram
https://www.quora.com/What-is-a-bigram-and-a-trigram-layman-explanation-please
https://web.stanford.edu/~jurafsky/slp3/3.pdf
http://www.cic.ipn.mx/~sidorov/Synt_n_grams_ESWA_FINAL.pdf