Table:
|  |  |  | Payments due by period |  |  |  |
| --- | --- | --- | --- | --- | --- | --- |
| (in thousands) | 2020 | 2021 - 2022 | 2023 - 2024 | 2025 and thereafter | Other | Total |
| Operating lease obligations (1) | 19,373 | 36,373 | 19,683 | 1,666 | - | $77,095 |
| Purchase obligations (2) | $24,800 | $8,129 | $438 | $ - | $ - | $33,367 |
| Liability for uncertain tax positions (3) | - | - | - | - | 5,386 | $5,386 |
| Investment commitments (4) | 1,754 | 205 | - | - | - | $1,959 |
| Total | $45,927 | $44,707 | $20,121 | $1,666 | $5,386 | $117,807 |
Paragraphs:
Contractual obligations
As of December 31, 2019, our contractual obligations were:
(1) See "9. Leases" in Item 8 of this Annual Report for additional information.
(2) Represents the fixed or minimum amounts due under purchase obligations for hosting services and sales and marketing programs
(3) We are unable to reasonably estimate the timing of the cash outflow due to uncertainties in the timing of the effective settlement of tax positions.
(4) Represents the maximum funding that would be expected under existing investment agreements with privately-held companies. Our investment agreements generally allow us to withhold unpaid committed funds at our discretion.
A detailed discussion and analysis of the fiscal year 2017 year-over-year changes can be found in Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations of our Annual Report on Form 10-K for the year ended December 31, 2018.
Question:
What does purchase obligations refer to?