'Saber' is used for knowledge of facts, information, or skills. 'Entender' is used for understanding ideas, explanations, or meanings at a given moment. The central difference is knowledge established versus momentary understanding. In a conversation, choosing the verb changes the focus of what you communicate.

'Saber' expresses that you know data, facts, names, times or addresses. It is also used to say that you know a language or a learned fact. Normally, 'saber' answers questions of the type 'what', 'when', 'where' or 'who'.

'Saber' is used to express that you have the ability to do something that is learned, such as a language, swimming, or playing an instrument. In Spanish, this idea usually goes with a verb in the infinitive after 'saber'. The phrase indicates learned ability, not understanding at the moment.

'Entender' is used to express that you understand the sense of something, such as an explanation, a text, a situation, or a person. Normally it refers to the mental process of grasping meaning, not to possessing a fact. You can use it to indicate that a message is clear to you at that moment.

With languages or texts, 'saber' indicates knowledge of the language or content, and 'entender' indicates that you understand what is said or read in a specific case. You can know a language but not understand a difficult sentence. You can understand a specific text without claiming that you know the whole topic.

In everyday interaction, 'Do you know...?' tends to seek information or confirmation of knowledge, and 'Do you understand...?' tends to ask whether the explanation or the message is clear. The choice changes the intention of the question. Using the correct verb prevents misunderstandings about what is expected as an answer.

'Saber' is irregular in the first-person present ('yo sé') and regular in many other present forms. These forms are used to talk about knowledge or ability in the present. Remembering 'yo sé' helps avoid common mistakes.

'Entender' is regular in 'yo' but changes the vowel e→ie in 'tú', 'él/ella/usted' and 'ellos/ellas/ustedes' in the present. These forms are used to talk about understanding in the present. The vowel change preserves clarity in quick conversations.

Use 'saber' to say that you have knowledge or ability. Use 'entender' to say that you understand a message, an explanation, or a situation in a concrete context. Choosing wisely communicates whether you are talking about knowing something or understanding it at that moment.