What is em?

Answer 1

It is a text tag in HTML and a unit in CSS.
In HTML it acts as an emphasized text.
In CSS it gives more flexibility to your measurements and your website would launch better in different devices.
For example 2 em equals 2 times of the size of a text.

Answer 2

For CSS

It is an unit of height , width etc. like pixel

1em means normal size displayed by browser. If you opt for 2em it will be 2x normal size and so on.

Hope this helps☺️☺️.

Answer 3

For HTML

Strong is used for text that has importance and also makes text bolder.

Bold is used for just making text bolder.

Italic is used for making text italic.

Whereas emphasize is used for making text italic and displaying text that has importance.

Hope this helps☺️☺️.