Makes a little more sense now.
This is a 457(b) plan, which is essentially a municipal government's version of a 401(k) retirement plan. You make contributions to it (this is what it means to defer compensation - you don't get taxed on your contributions), pick among the available investment plans, and don't start withdrawing until retirement.
The county does not match your contributions (as some employers do) as per the FAQ, so that makes the plan somewhat less appealing. They make you call or log on to a system to see the plans they offer, so I don't know if they're any good.
A 457(b) without matching actually works similarly to an IRA: you make contributions, get to deduct the contribution from your taxes, invest it, and pay taxes on the money you withdraw after 60. The difference is that the 457(b) plan allows you to contribute up to $17,000 and it's fully deductible regardless of your income. A traditional IRA allows you to contribute only $5,000 per year and if you are single, not all of it is tax deductible with an income above $56,000.
For completeness' sake, there is also the Roth IRA. Your contributions are not tax-deductible, but your withdrawals (after age 60) are. Singles can make full use of this if their income is below $110k. So all those capital gains... well, you won't pay taxes on them. This is a really good deal for young people especially. The limit is also $5,000 per year and it's shared with the traditional IRA. (So you could contribute $2k to the traditional IRA and $3k to the Roth IRA, but not $5k to both.)
Now, to answer your question: let's assume you're single, in your 20s/30s, and your income is below $110k. As a first step, I'd probably max out the Roth IRA. Yeah, you don't get the tax deduction now... but in 30 years, most of the value from your current contributions is going to come from capital gains. Assume an 8% average rate of return, for sake of argument, and a contribution of $5,000. After 30 years, your account would have a value of $50,300. You didn't get a tax break on those $5k, but you're not paying taxes on the other $45k. That's a pretty awesome deal.
$5,000/year is, unfortunately, way too little to save for retirement. The question now is whether you should save the remainder in your 457(b) plan or in a regular, taxable account. This is going to depend largely on the funds offered by your employer. You should check if they have a low-cost target date retirement fund that is made up only of index funds. Given that the plan is offered by Prudential, I think this may not be the case. If so, it's worth thinking about just making contributions to a regular, taxable account instead. You lose money upfront (since it's not tax exempt), but will make up for it over all the years you pay lower fees. You'll also pay only the capital gains tax when you sell your investments, which is lower than the income tax.
As a reference: you should try and save 20% of your income for retirement. More is better, but less can be problematic. Early on in your career, that may be difficult - and it's ok to start saving a little later. Calculations showing the benefit of saving early vs. saving longer are nonsense, because they don't account for inflation and rising incomes (it's easier to save $100 in 5 years than saving $100 today). Just don't postpone saving for too long.