In a relative manner; often used when comparing lists, where the term denotes that the items in the lists correspond to each other in the order they are given
Serena Williams and Roger Federer won the women's and men's singles titles, respectively, at the 2010 Australian Open.
Respectively means in the same order as the items that you have just mentioned. Their sons, Ben and Jonathan, were three and six respectively. in the same order as the things you have just mentioned