In loose terms, a Latina/o is someone who can trace their roots to Latin America. Although many people use the terms Latina/o/x and Hispanic interchangeably, others argue for the use of one or the other; the preference is often regionally influenced.
Latina is the feminine form of the word, and Latino the masculine. In recent years there has been a push to use more inclusive forms of the word instead of using the male Latino as the default. In addition to the “a/o” rendering, you may also see the use of Latinx, which seeks to avoid binary gender identification.
It is important to note that Latinx is not a racial identifier, but an ethnic one (although it is not a single ethnicity, but a collection of ethnicities.) Therefore, some Latinx might identify themselves by both their race and their nationality/ethnicity.