What is the meaning of practical services?

Different process of gadgets and machine? How do you estimate rcc roof slab? What is mpa of concrete? Is planned a past tense or a future tense? What is galvanic isolation transformer? I want to learn how to program? What is air gap in case of transformer? What does C stand for in temperature? How do you change the frequency on a radio controlled car? What technologies are used in mining? What term best defined as to assemble for public purpose? Purpose of web services? Five 60 ohm resistors are connected in parallel What is their equivalent resistance? How did the internal combustion engine change America? What does greater capital mobility mean? Is there any reason for a new radiator to leak other than faulty build? Which flowchart symbol indicates the need to make a decision? How distributed information system helps global organization? What is meant by entry controled loop? Where synchronous motors used in ship?