Above all regalia that a Mason wears the apron is most likely the most iconic. It's origins go back to the original Stonemasons that Freemasonry draws a lot of its ritual and ceremony from. However as time has passed and those members of masonic lodges are no longer operative Masons, but rather free and accepted or speculative we now use these symbols elsewhere in our lives.
The apron of the Entered Apprentice is a plain white apron normally made of lambs leather and is presented at the first degree ceremony. It's plain white appearance is a symbol of the early stages of the masonic journey. As the Mason progresses to the second degree or that of a 'FellowCraft' then the apron becomes more decorated to show they have gained experience - much in the same manner that the original Stonemasons would have identified seniority amongst their own trade. Finally on completion of the third-degree or that of a Master Mason then the apron changes considerably; it is more ornate with symbology and decoration.
The apron itself is made of geometric shapes which all have a relevance in masonic knowledge and advancement and the decorations themselves in the borders, rosettes and tassels all have a story to tell which make up part of the ritual and ceremony experienced in Freemasonry.
Finally once the Master Mason makes his journey to the Worshipful Masters chair then he is awarded a new apron which is a variation of the Master Masons apron where the rosettes are changed for levels to denote rank, experience and knowledge. It can take many years for a new initiate to make their way through to the Worshipful Masters chair in a lodge and through that time the aprons are worn with ultimate pride and reverence. A Mason will have special cases to transport their aprons (they may have multiple depending on the order that they belong to and their role in that order) so they are kept in good condition and to pay respect to the badge of a Freemason.