If you have purchased a scanner, you may already have such software installed on your computer. Look for controls that are readily accessible. Size and portability. Inkjets are generally small in size, but there is a definite difference among the models. Several have hidden folding and pull out paper trays that make them great for transporting or tucking away in small work spaces.
Some models are even smaller.
You can take them almost anywhere. Interface really describes how the printer is attached to your computer. The USB connection is particularly useful if you need to print 50 or more pages at a time, or want to use your computer while it's printing. This is the ability to print on both sides of the sheet, automatically. Using an inkjet, you will have to do this manually.