When you select the search box on the taskbar, Cortana will help you find things and get things done.
Type what you're looking for, or select the microphone next to the search box if you'd rather say it. (Your PC needs to have a microphone for you to talk with Cortana.)
Better yet, just say "Hey Cortana" then ask your question...say:
Hey Cortana...Is it going to rain today
Hey Cortana...What's on my schedule for today
Hey Cortana...Give me a Chicken and Dumpling recipe
Hey Cortana...Send email to...
Hey Cortana...Open WORD
Hey Cortana...How many ounces in a gallon