There are seas on Earth, Moon, Mercury, Mars, but this geographical and astronomical term refers to different formations.
The seas on Earth are depressions filled with water. The seas on the Moon are lowlands, located mainly on the visible side of the satellite and filled with lava with an albedo lower than mountainous regions. The seas on Mercury and Mars are areas of the surface that are less reflective than other regions. There is no connection with the terrain. There is no liquid water in unearthly seas.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.