To answer the question, lets refer to the website globaleconomy.com. It explains the term "currency crisis" this way:
"A currency crisis, also called a devaluation crisis or an international financial crisis, is a sharp depreciation of the currency of a country. The depreciation usually comes after a period during which the exchange rate has been very stable, even fixed. "
It gives Mexico in 1995 as an example, when the Mexican Peso declined by 100 % in one year, from 3 pesos to a dollar to 6 pesos to a dollar.
Thus, a currency crisis is a sharp sudden decline on a currency`s value. But what woukd that mean to businesses? Taking the example of the Asian financial crisis in 1997, the sharp drop of the peso from 26 to 30 pesos to the dollar bloated import costs. Industries were unable to fund their raw material imports due to diminished value of their funds, driving them to shut down and lay off workers.
On the other hand, the decline we are experiencing is gradual, and our manufactueing sector has instead, grown.
In a Philippine Star Article, Unionbank economist Ruben Carlo Asuncion explains that the strong dollar and the current trade war between the US and China and emerging market turmoil in Turkey and Argentina are to blame for the struggles of the peso in global currency markets.
Large investors buy dollars, which are seen as a safe currency for hedging when there is an economic crisis like a trade war or major recession. With this, it is also worth noting that other Asian currencies such as the Indonesian Rupiah and the Indian Rupee have devalued by even more, owing to the same factor.
All that said, any declines in value are often prompted by external rather than domestic factors, where global investors will buy more US dollars, making it scarce, and therefore, more expensive than other currencies. This makes the other currencies value go down. To simply blame governments for a currency devaluation is too simplistic, and only feeds baseless political noise.
Likewise, this is gradual, enabling central banks to manage the decline. Central Banks often resort to buying pesos with their dollar reserves to stabilize the value of the peso and prevent steep and drastic changes in value.
But it cannot do that for too long and too much. The peso like other currencies needs to be traded and its value will depend on how well it is traded, not how much government tries to keep it stable. Government has other important uses for its gross international reserves.