All the gifts Paul mentioned in Romans 12:6-8 need exercising within the body of Christ for its members" mutual benefit (cf. Romans 12:5). Obviously other gifts have other purposes. However, Paul was stressing here the need to recognize that the members of the body contribute to the common welfare. In each case he spoke of the way we use these gifts. [source][source][source]
"Service" or "serving" ( Romans 12:7, Gr. diakonia) probably refers to ministering to the material needs of other believers. [1] Teaching involves explaining what God has revealed (cf. 1 Corinthians 14:6). It differs from prophesying in that prophesying (from propheteuo, lit. to speak forth) evidently included communicating any word from God, inspired or uninspired ( 1 Corinthians 12:28; Ephesians 4:11). [2][source]
"Exhorts" or "encouraging" translates the Greek word parakalesis (cf. Romans 12:1), sometimes rendered "comfort." All three words are good translations. The context provides the clue to the main idea wherever the word appears. Here exhortation is perhaps best. Whereas teaching appeals to the mind, exhortation (preaching) appeals to the will. "Giving" is capable of broad application within the body. We should practice giving with singleness of heart, namely, freedom from mixed motives (cf. Acts 5:1-11). The idea is not so much giving lavishly as giving single-mindedly, to please the Lord. [source][source][source]
Leaders experience temptation simply to enjoy the benefits of their positions rather than really providing leadership by serving. Showing mercy relates to ministering to the sick and specially needy. A cheerful rather than a grudging attitude is an important part of such ministry. [source][source][source]