Modern English has 'biological-' or 'natural-gender' marking, i.e. only a restricted number of living things are distinguished for gender. This is different from other language (including Old English) which have 'linguistic gender' - everything has gender: tables, chairs, houses etc.
Gender in English is only marked on nouns and pronouns. Pronouns take different forms (e.g. he, she, it). Nouns can take either different forms, or can be distinguished by specific morphemes. Examples of nouns that take different forms: mother vs. father, boy vs. girl, bull vs. cow, bridegroom vs. bride. Examples of nouns that distinguish gender by morphemes: host vs. hostess, lion vs. lioness, hero vs. heroine, widower vs. widow)