Thermite is a mixture of aluminum metal $Al$ and iron(III) oxide. Here is the thermite reaction triggered by the combustion of a magnesium wick.
It is a redox reaction where aluminium is oxidised and iron reduced: $Fe_2O_3$ $+$ $2Al$ $\longrightarrow$ $2Fe$ $+$ $Al_2O_3+$
The iron product of this reaction is liquid at temperatures produced exceeding $2000^oC$ Fifty years ago, non-welded rail trains caused an unpleasant noise in trains:
The aluminothermy is used to weld railway tracks, thus reducing noise and increasing performance:
See here the real work:
Video is due to - → Wolfgang Lendner and Jan Olsson