Why a log scale?
On a normal (linear) chart, early Bitcoin moves look flat and recent moves look enormous. A logarithmic scale shows percentage changes at the same size, so a move from $3,000 to $6,000 looks as big as a move from $50,000 to $100,000. That makes long-term trends and cycles much easier to compare.
The 200-week moving average
The 200-week MA is the average closing price of the last four years — roughly one full Bitcoin halving cycle. In past bear markets the price has bottomed close to this line, which is why many long-term investors watch it as a “floor”. The 50-day MA shows the short-term trend.