In a wider sense, "yoshoku" refers to the cuisine of Western countries in Europe and the United States. In Japan, however, the Western dishes served at "yoshokuya" - restaurants serving Western cuisine - are arranged in a Japanese style and have been so adapted to the Japanese taste that it hardly can be called Western cuisine anymore.
In general, this type of food is popular among children and young people. A very typical dish is "kare raisu," or curry rice. Curry was introduced to Japan from India and consists of curry sauce served on top of cooked white rice. In Japan, it is a typical lunch dish, but can also be eaten for dinner. Another popular food in Japan is "korokke," or corquettes. They are made by mashing potatoes, mixing them with ground meat and onions, and shaping them into round, flat cakes. Then they are coated with flour, egg, and bread crumbs, and fried in oil. Of course you can have korokke in Western-style restaurants, but you can also buy them from some butchers that sell them as oyatsu (snacks) or okazu (side dishes). It can be nice to enjoy a freshly fried korokke while strolling around. There are many variations of korokke, and depending on their filling they are called pumpkin korokke, rice korokke, and other terms. Korokke filled with bechamel sauce are called cream korokke. They are also sold in large quantities as a frozen food. Another dish that many yoshokuya specialize in is "omurice." Basically, omurice is just an omelette wrapped around chicken rice. It is an original Japanese recipe. The chicken rice filling can have a variety of flavors, such as ketchup or salt and pepper. It is a dish that is often made at home. The chicken rice is placed on top of an omelette in a pan, quickly flipped over, and served on a plate. At home you can have fun with the tomato ketchup by drawing patterns on the omelette. In many specialty restaurants, they try to think of ways to add their own twist to the ingredients of the rice or the topping sauce. Besides ketchup, demi-glace sauce, bechamel sauce, and stew are also often used as topping sauce. Some places even put on some kind of performance by placing a soft-boiled egg on top of the chicken rice, inserting a knife in the center, and spreading the egg. There is a dish similar to curry rice called "hayashi rice." Thin slices of beef and onion are stir-fried and put on cooked white rice together with a sauce similar to demi-glace. Since it is not as spicy as curry, it is popular among children and adults alike. A type of pasta that is often eaten at Western restaurants is spaghetti. Many places have spaghetti dishes you won't find in Italy, such as tarako (cod roe) spaghetti, natto (fermented soybean) spaghetti, and other Japanese-style spaghetti. There are many other Western-style dishes that have been adapted to the Japanese palate, such as "hamburgers", "fried shrimp", "stew", "gratin", "doria", which is pilaf topped with gratin and then baked in the oven, or "cabbage rolls", which is ground meat wrapped in cabbage and stewed in tomato sauce, etc..