An ideal machine is a theoretical construct that operates without any energy losses, whereas real machines inevitably experience energy losses due to factors such as friction and air resistance.

In theory, an ideal machine is a device that performs work with complete efficiency, meaning that all the energy supplied to the machine is converted into useful work output. However, it is important to note that no machine can achieve this ideal state in practice. Real machines always experience some degree of energy loss, which is often transformed into heat or other non-useful forms of energy.

The efficiency of a machine is defined as the ratio of useful work output to the energy input, expressed as a percentage. An ideal machine would have an efficiency of $100\%$, indicating that all the input energy is successfully converted into useful work. In contrast, real machines have efficiencies that fall below $100\%$ due to unavoidable energy losses. The efficiency of a real machine can be calculated using the following formula:

For instance, consider a machine that requires $1000$ Joules of energy input to produce $800$ Joules of useful work output. Its efficiency can be calculated as follows:

In summary, while the concept of an ideal machine represents a scenario with no energy losses, real machines invariably experience energy losses due to friction and other factors, resulting in efficiencies that are always less than $100\%$.