First – a weed to me is any group of plants growing where you don’t want them, or crowding out other more desirable plants.
Second – not all weeds are invaders from other places. Most are natives.
Third – these are very important plants for restoring disturbed areas. I call them nature’s “first responders”. They are almost all annuals (must grow from seeds each year as last year’s die and don’t come back).
Their job