Your old and beaten up
Whether it be a lightweight mid-cut boot or full height heavy-duty trekker, a boot is going to provide more support and offer better protection than a regular shoe. A boot is particularly important when carrying a load on your back as they are generally manufactured with denser foams, thicker rubber soles and heavier duty upper to withstand the rigours an extra 15-20 Kg of gear places on your feet. A boot is generally heavier and takes a little longer to break in that a shoe and are best suited to users on extended treks or particularly long day walks.
Walking shoes that are designed for hiking provide good stability on the trail. They are not as soft and forgiving as that comfy pair of joggers in your cupboard, but they will offer more protection against uneven and rough terrain not to mention better grip and increased levels of durability. Shoes for hiking are made with a range of materials from heavy duty leather uppers to super lightweight mesh. If you need some comfy and supportive treads for a day of adventure or your morning walk that takes you a little further than the duck pond at the end of the street, then a supportive pair of hiking shoes is what you need.
Shoes made for trails are a cross between a durable hiker and a soft and forgiving road running shoe. A trail runner offers more torsional rigidity to cater for uneven ground and has extra forefoot protection against stones. Many lightweight hikers will opt for a trail running shoe, trading off the durability of a hiking shoe for the lightweight construction of a runner.
Sandals have a range of uses, and there are different styles aimed at each. If it's for travel and urban wear, a low profile and lightweight sandal will keep you comfortable and often come with some style that won't make you look like a tourist. However, if you're after something that will give you some grip on the trail, maybe for use around a river or in the boat, then a sandal with a supportive midsole will almost mirror the support and protection offered by hiking shoes.
Shoes aren't cheap, and they are possibly put through the toughest regime of any item of clothing we don every day which means they are often the item we replace the most. So a little love and care