Inflation is good for borrowers, employers and sellers. Deflation is good for lenders, employees and buyers.
Borrowing - Inflation: I borrow $1000.00 today at 3% with an inflation rate of 2% (per year). At the end of this year I pay the loan back in full at $1030.00. I have spent a larger nominal value, however the real value of the loan is now $1030.00 * 0.98 = $1009.40. Meaning my effective interest rate was around 1%.
Borrowing - Deflation: Let's take the same numbers, but now it's 2% deflation. I pay back the loan, $1030.00 nominal value. The real value is $1030.00 * 1.02 = $1050.60. My effective interest rate is around 5%.
Salary - Inflation: I am paid $100,000 this year for my work, inflation rate of 2%. Without a pay raise my nominal salary remains the same next year, but my real salary becomes $98,000. This is a pro for employers, I am a cheaper employee. It's a con for me, my time is worth less.
Salary - Deflation: I am paid $100,000 this year for my work, deflation rate of 2%. Without a pay raise my nominal salary remains the same next year, but my real salary becomes $102,000. This is the reverse. I cost my employer more, but without changing nominal salaries my time has become more valuable.
Purchasing - Inflation: You want a widget worth $1000.00 today and face 2% inflation. If you purchase it at the start of the year, ignoring depreciation on the widget, it's worth $1020.00 at the end of the year. So if you resell it at that point you've made 2% (nominal), though the real value is the same.
Purchasing - Deflation: Using the same widget, price and 2% deflation. If you purchase it at the start of the year for $1000.00, and sell at the end for $980.00 you end with the same real value, but you've lost 2% of the nominal value. Barring a need to purchase an item within a particular time, it makes sense for purchasers to delay purchasing as long as possible. On the other hand, vendors want to sell as early as possible because the nominal value of their goods are decreasing (and this ignores other costs of holding inventory).