A garden tiller is a powerful tool used to prepare soil for planting by breaking up hard, compacted ground, removing weeds, and mixing in amendments like compost. It's essential for establishing new garden beds, rejuvenating existing ones, or preparing lawns for reseeding or new sod. Tillers come in various types, including front-tine and rear-tine models, with rear-tine tillers typically being more powerful for larger or more compacted areas.