This is commonly called Bangkok Metro.  Blue Line opened in 2004.  This line is a mixture of underground railways and elevated railways.  The purple line opened in 2016.  This line is elevated railway all.
These two lines intersect at Tao Poon station.  Eating and drinking inside the station or in the car is prohibited.  There are several types of tickets, so please check in advance.(Prepaid card, one-day pass card, three-day pass card, token)  The ticket gate is an automatic ticket gate.  Fares are more expensive than buses, but it is a convenient transportation to get around major tourist destinations.