Gendered language is language that assigns gender to the subjects or topics at hand. It generally assumes a gender that exists on the male/female gender binary. This is problematic as it excludes people who do not exist on that binary.
More About Gendered Language
An example of gendered language in action would be someone giving sex advice and refers to one partner as "he" and the other as "she"; this assumes heterosexual pairing and makes their advice inaccessible to the many other partners out there who identify differently. The use of gender neutral language, such as the word "partner" or "they" instead of a gender specific pronoun, can help make writing and speech more inclusive.