What does "thumbs" mean?

English Language Tests, Intermediate level

ESL/EFL Test #723 [color=blue]“Real Life: Using Body Parts as Verbs (3)”, question 5

My father loves to read the newspaper every morning. Every day, as he sips his morning coffee, he slowly through each page of the paper.

(a) knees
(b) thumbs
© arms
(d) faces

English Language Tests, Intermediate level

ESL/EFL Test #723 [color=blue]“Real Life: Using Body Parts as Verbs (3)”, answer 5

My father loves to read the newspaper every morning. Every day, as he sips his morning coffee, he slowly thumbs through each page of the paper.

Correct answer: (b) thumbs

Your answer was: [color=green]correct
[size=200]_________________________[/size]

What does “thumbs” means here?

.
Browse, read.
.

thanks Mister Micawber, your explanation is very concise and clear.Regards