This paper reviews recent progress in exploring magnetocaloric materials, focusing on the LaFe₁₃₋ₓSiₓ alloys with a first-order magnetic transition. These alloys exhibit large entropy changes near room temperature. The effects of magnetic rare-earth doping, interstitial atoms, and high pressure on the magnetocaloric effect (MCE) have been systematically studied. Special issues such as determining the MCE associated with the first-order transition, magnetic and thermal hysteresis, and magnetic exchange in these alloys are discussed. The applicability of giant MCE materials for magnetic refrigeration near ambient temperature is evaluated. Other materials with significant MCE are also briefly reviewed. The MCE is a unique way to achieve refrigeration from ultra-low to room temperatures. It involves magnetic entropy changes that are crucial for refrigeration efficiency. The MCE was first discovered by Warburg in 1881 and has since been studied extensively. The first magnetic refrigeration experiment was conducted by Giauque and MacDougall in 1933, achieving temperatures below 1 K. Today, magnetic refrigeration is a key technology for ultra-low temperatures. The LaFe₁₃₋ₓSiₓ alloys show a first-order magnetic transition and large entropy changes. The Curie temperature increases with Si content, and the saturation magnetization decreases. The MCE in these alloys is significant, with entropy changes up to 20 J/kgK. The first-order nature of the phase transition is confirmed by the absence of hysteresis and the presence of "S"-shaped isotherms. The MCE is enhanced by doping with Co, Pr, or Nd, which shifts the Curie temperature to higher temperatures without significantly reducing the entropy change. The MCE is also influenced by interstitial hydrogen and carbon, which can increase the Curie temperature and enhance the entropy change. The magnetic exchange in these materials is strongly dependent on the Fe-Fe distance and the type of rare-earth element used. The MCE near the first-order phase transition is evaluated using the Maxwell relation and heat capacity methods, revealing the importance of considering magnetic domains and phase coexistence. The results show that the MCE is significantly affected by the first-order phase transition and the interplay between magnetic and thermal effects.This paper reviews recent progress in exploring magnetocaloric materials, focusing on the LaFe₁₃₋ₓSiₓ alloys with a first-order magnetic transition. These alloys exhibit large entropy changes near room temperature. The effects of magnetic rare-earth doping, interstitial atoms, and high pressure on the magnetocaloric effect (MCE) have been systematically studied. Special issues such as determining the MCE associated with the first-order transition, magnetic and thermal hysteresis, and magnetic exchange in these alloys are discussed. The applicability of giant MCE materials for magnetic refrigeration near ambient temperature is evaluated. Other materials with significant MCE are also briefly reviewed. The MCE is a unique way to achieve refrigeration from ultra-low to room temperatures. It involves magnetic entropy changes that are crucial for refrigeration efficiency. The MCE was first discovered by Warburg in 1881 and has since been studied extensively. The first magnetic refrigeration experiment was conducted by Giauque and MacDougall in 1933, achieving temperatures below 1 K. Today, magnetic refrigeration is a key technology for ultra-low temperatures. The LaFe₁₃₋ₓSiₓ alloys show a first-order magnetic transition and large entropy changes. The Curie temperature increases with Si content, and the saturation magnetization decreases. The MCE in these alloys is significant, with entropy changes up to 20 J/kgK. The first-order nature of the phase transition is confirmed by the absence of hysteresis and the presence of "S"-shaped isotherms. The MCE is enhanced by doping with Co, Pr, or Nd, which shifts the Curie temperature to higher temperatures without significantly reducing the entropy change. The MCE is also influenced by interstitial hydrogen and carbon, which can increase the Curie temperature and enhance the entropy change. The magnetic exchange in these materials is strongly dependent on the Fe-Fe distance and the type of rare-earth element used. The MCE near the first-order phase transition is evaluated using the Maxwell relation and heat capacity methods, revealing the importance of considering magnetic domains and phase coexistence. The results show that the MCE is significantly affected by the first-order phase transition and the interplay between magnetic and thermal effects.