A burner, comprising: a housing defining a housing cavity, wherein an air inlet is defined in a lower part of the housing 1 and a burning port is defined in an upper part of the housing, and the air inlet and the burning port are in communication with the housing cavity; and at least a burner unit arranged in the housing cavity, wherein a burning fire hole exposed from the burning port is defined in an upper part of each of the at least one burner unit, and an internal gas channel is defined in each of the at least one burner unit to allow a part of air entering from the air inlet to flow to the burning fire hole through the internal gas channel, wherein the burner has an external gas channel provided at an outer side surface of each of the at least one burner unit, the external gas channel being in communication with the air inlet and the burning port to allow an other part of the air entering from the air inlet to flow to the burning fire hole through the external gas channel, wherein the housing comprises: a side enclosing plate, wherein an installation space penetrating in the up-down direction is enclosed by the side enclosing plate, allowing a burner unit of the burner to be installed in the installation space; an air distribution plate disposed at and sealing a lower end opening of the installation space and is configured to be located below the burner unit, characterized in that a first air inlet and a second air inlet for air inflow, are defined at the air distribution plate and spaced apart from each other, wherein the first air inlet is in communication with the internal gas channel in the burner unit, the second air inlet is in communication with the external gas channel located at a side portion of the burner unit 2. a housing defining a housing cavity, wherein an air inlet is defined in a lower part of the housing 1 and a burning port is defined in an upper part of the housing, and the air inlet and the burning port are in communication with the housing cavity; and at least a burner unit arranged in the housing cavity, wherein a burning fire hole exposed from the burning port is defined in an upper part of each of the at least one burner unit, and an internal gas channel is defined in each of the at least one burner unit to allow a part of air entering from the air inlet to flow to the burning fire hole through the internal gas channel, wherein the burner has an external gas channel provided at an outer side surface of each of the at least one burner unit, the external gas channel being in communication with the air inlet and the burning port to allow an other part of the air entering from the air inlet to flow to the burning fire hole through the external gas channel, wherein the housing comprises: a side enclosing plate, wherein an installation space penetrating in the up-down direction is enclosed by the side enclosing plate, allowing a burner unit of the burner to be installed in the installation space; an air distribution plate disposed at and sealing a lower end opening of the installation space and is configured to be located below the burner unit, characterized in that a first air inlet and a second air inlet for air inflow, are defined at the air distribution plate and spaced apart from each other, wherein the first air inlet is in communication with the internal gas channel in the burner unit, the second air inlet is in communication with the external gas channel located at a side portion of the burner unit 2. a side enclosing plate, wherein an installation space penetrating in the up-down direction is enclosed by the side enclosing plate, allowing a burner unit of the burner to be installed in the installation space; an air distribution plate disposed at and sealing a lower end opening of the installation space and is configured to be located below the burner unit, characterized in that a first air inlet and a second air inlet for air inflow, are defined at the air distribution plate and spaced apart from each other, wherein the first air inlet is in communication with the internal gas channel in the burner unit, the second air inlet is in communication with the external gas channel located at a side portion of the burner unit 2.