Cypress different between using .focus() and not using it

[AndreeMeilio]

Hi,
I am new at automation test using cypress, i'm just curious what's the different between writing a test with .focus() and .blur()
e.g cy.get("#loginUsername").focus().type("admin").blur()
and not using it
e.g cy.get("#loginUsername").type("admin")
I tried both of those and it ran the same. so what's the different?