We can activate labeling by going to Layer Properties | Labels, selecting Show labels for this layer, and selecting the attribute field that we want to Label with. This is all we need to do to display labels with default settings. While default labels are great for a quick preview, we will usually want to customize labels if we create visualizations for reports or standalone maps.
Using Expressions (the button that is right beside the attribute drop-down list), we can format the label text to suit our needs. For example, the NAME field in our sample airports.shp file contains text in uppercase. To display the airport names in mixed case instead, we can set the title(NAME) expression, which will reformat the name text in title case. We can also use multiple fields to create a label, for example, combining the name and elevation in brackets using the concatenation operator (||), as follows:
title(NAME) || ' (' || "ELEV" || ')'