Please help me out, I cannot get the brush back that can add/remove background

[dust92]

I need help with re-creating the situation where I can use a brush to add/remove/refine the background pixels after a foreground selection. When I choose brush, I can only brush colors. When I (re-)choose foreground selection, I can see this lasso and can make a selection but I cannot get the magical brush back that can feather the edges and add/remove background. What am I doing wrong. Three hours, I am sorry for this stupid questions, totally stuck.