How to convert a line to points?

The Vector -> Geometry Tools -> Extract Nodes tool will generate a point layer shapefile with points at each vertex of each line.

If you want specific points; say start and end of lines, In QGIS 3.0, you have a tool called "Extract specific vertices", in which you can mention 0,-1 as vertex indices to get start and end point of each line. In case you need representative samples of line at some user specific distance, then "Locate points along lines" plug in can be used. This QGIS alternate for construct point tool in Arcgis.