Thermodynamics is a word which originates from word $therme$ menaing heat and $dynamic$ meaning force
$$thermodynamics = therme + dynamic$$This bifurcation comes from the classical history of themodynamics days. In primitive days, understanding of thermodynamics centered around the concept of getting power from hot bodies, or abilities of hot bodies to produce work. This happens to be partly the scope of today's total scope.
Thermodynamics is encountered in our daily life, in all corners of physics. Some processes are spontaneous and there are some which we make it to happen. But none of the are random or happen in a arbitrary way. There is always a rhythm for all physical processes to occur in nature. Even the random motions of molecules have typical correlation coefficients or correlations (that way statistical properties are defined). Another example is turbulence in fluid flow. Everything happens with directional constraints.
Mechanical Engineering can be converted into inter molecular energy but reverse in not possible. Certain processes can happen in both directions like heating and cooling of a gas but in such scenarios, there is change in external surroundings. If we exclude mass energy conversion priciple ($e = mc^2$) we have $mass + energy = constant$. Thermodynamics is a fundamental subject that describes the basic law governing the occurence of physical processes associated with transferor or transformation of enerygy
Conversion or energy is not efficient in all directions.We can have $100\%$ converion from mechanical energy into elelctrical energy and vice versa but $100\%$ conversion pf heat into work in not possible even in ideal case.
There are directional constraints on the process of transformation (on conversion of energy taking (takes) place). Thermodynamics guides these principles. the realtionship between physical properties of the systems by these processes is alo established by thermodynamics. Thermodynamics also establishes the different physical properties which are being affected by these processes. Entire subject of thermodynamics is based on laws of nature formed by observation, common experience, or experimental observation.
There are two views in thermodynamics i.e., macroscopic and microscopic. Macroscopic view is classical while microscopic view is statistical. In macroscopic view, attention is at matter or substance level. Macroscopiv view specifies characteristic features of the system. These features should be able to sensed and measured. If they cannot be sensed or measured, characteristics can atleast be related by some expressions with primary characteristics.