Big red tomatoes probably started their life being small, yellow and rough-skinned. This South American native began to travel the world courtesy of Spanish colonisers who first took them to their Caribbean claims. Next stop was the Philippines and then into South East Asia, from where the tomato continued to spread in popularity.
Thanks again to the Spanish, they were introduced to Europe in the 1500s. At first considered to be poisonous (they are a member of the deadly nightshade family), they were used as decoration. This thinking changed somewhere along the line, as in France they gained aphrodisiac associations.
Years of hybridisation have yielded the tomato we know today, and this ever-useful ingredient has inveigled its way into the world's kitchens.
Yes, a tomato is botanically a fruit, as are eggplants, cucumbers, courgettes and pumpkins, but we know it as a vegetable and use it as such. We eat it raw, cook it, bottle it, can it and turn it into pastes. Most home gardeners grow it. I do with various success, now only bothering with well-known cultivars after seeing the heirloom varieties succumb to pests and disease.
Available all year round, tomatoes are best eaten fresh in summer. The rest of the year you will get better flavour from a can.