Budget is the scheme of income and expenditure for a certain period of time, allowing to plan finances. Typically, budget is divided into budget items, each of which regulates movements of funds for a certain category of income or expenditure.
Primitive approach to the budget consists in controlling expenses so that they do not leave the previously designated box, but with proper approach, budget can be a means of detailed planning and study of financial flows.
Most of revenues and expenses has the stable nature, repeating from month to month with virtually no changes.Typically, this is salary, urgent expenses or funds being put aside for certain purposes (for example, for holiday). However, there is a significant part of "spontaneous" expenses or revenues, which are irregular and poorly subject to planning. When stable and unstable parts of the budget are considered together, it is difficult to build reliable plans and to find trends in your financial life.
That is why tr.en.d implements a two-level system of budget. The basic level contains general budget, which serves for long-term planning of finance.