1. A method for providing a context-aware service of a user device, the method comprising: receiving, by an input unit of the user device, a first user input according to a guidance provided by the user device, the first user input being at least one of a natural language-based text input or a natural language-based speech input; in response to receiving the first user input, parsing the received first user input to extract and identifying a condition, an action corresponding to the condition, and a command, wherein the action is a function executable by one or more applications of the user device; defining a rule including the condition and the action corresponding to the condition based on the parsed first user input; mapping the command to the rule in response to the defining of the rule; storing the rule and the mapped command in at least one of the user device or a server; receiving, by the input unit, a second user input, wherein the second user input is one of a natural language-based text input or a natural language based speech input; and in response to receiving the second user input: determining whether the second user input corresponds to the command; activating, if the second user input corresponds to the command, the rule to detect, by a sensor of the user device, a context of the user device; and executing, if the detected context corresponds to the condition of the rule, the action corresponding to the condition.