noun
firewood; fuel for a fire
General term for material burned as fuel, such as wood, leaves, or other combustibles.
冬に備えて焚き物を集める。
I gather firewood in preparation for winter.
薪 specifically refers to split logs or firewood, while 焚き物 is a broader term for any combustible material used for burning.
Compound of 焚き (taki, the continuative form of 焚く 'to burn') + 物 (mono, 'thing').