This line absorbs foreign exchange effects, gains on selling a building, insurance recoveries, and marks on investments. It is genuinely miscellaneous, which is why a quarter can beat on eps with no operational improvement at all.
When it is large relative to operating-income, read the footnotes. Recurring items hiding in "other" are a classic way to make the core look cleaner than it is.
Example: Northwind reports a $16M gain on the sale of an old plant inside other income. That is 13% of the year's $120M operating income and will not repeat, so a forecast built on this year's net income starts $16M too high.
Related: operating-income, one-time-charge, pre-tax-income