The given reaction is a <u>redox reaction</u> because there's a <u>transfer of electron</u> from <u>Sodium</u> (Na) to <u>chlorine</u> (Cl)
where sodium is <u>oxidized</u> (due to loss of electron) and chlorine get <u>reduced</u> (due to gain of electron).
2. <u>Sodium</u> is a <u>highly reactive</u> element which belongs to the 1st group of periodic table, hence it can catch fire if it is kept free in atmosphere. so in order to prevent that it is stored in <u>kerosene</u> oil, which doesn't let Sodium come in contact with air .