You can sort your search by relevancy or title to the right of the screen. By default search results are arranged in relevancy order unless you chose another sort order from the advanced search screen. Results from browse categories display results alphabetically by title.
Sort by Relevancy: Search results are arranged in order of relevance to your search terms. The most relevant result will be first. Although several factors are involved in determining relevancy, the more times your search terms appear in the metadata or the transcript of a result, the higher it will be ranked in relevancy.
Sort Results by Title: The Title sort sorts all results alphabetically by title.